Patent Document 1 discloses a cartridge type of a magnesium air battery, as an example of a magnesium air battery, which active material is oxygen in the air as a cathode, and magnesium as an anode. Specifically, in the magnesium air battery described in Patent Document 1, each end of the magnesium film is connected to the pair of reels, and along with the magnesium film being wound by rotating the reels, magnesium films between the reels will generate power in cooperation with the cathode, which is located in the vicinity thereof.